Rolling bed press



s. B. MocLocKLlN ETAL. 3,168,034

ROLLING BED PRESS Feb. 2, 1965 Filed OGb. 28, 1963 3 Sheets-Sheet 1 Feb. 2, 1965 S. B. MCCLOCKLIN ETAL ROLLING BED PRESS 3 Sheets-Sheet 2 Filed Oct. 28, 1963 INVENTORS DOA/AID d' MPLAN, SIfMz/fz E M'froc'Z/:bv

Feb. 2, 1965 s. B. MccLocKLlN ETAL ROLLING BED PRESS 5 Sheets-Sheet 5 Filed Oct. 28, 1963 @l- N m ,f f NNN N Ww EP aia m J @y NQ WWI. b9 wm Mm. my Hl..||l|l.||||.||ll||||||Ul||||\...HHHH.. HHHHHUL; -MY @mfg 1111 i Q v wv h. NWN NNN www mmh QQ NNNN NMN m N NN -l m NMW|= N\N z A QNMWM." QQ QQ NN. NMMN www MN m NNN Unitd itigd Patented Feb. 2, i965 3,168,034 Roi-.Lino snp ranas Samuel B. McClochlin and Donald d. Kaplan, watonna, Minn., assiguors to The Owaonna Tool Company, watonna, Minn., a corporation of Minnesota Filed Get. 28, 1963, Ser. No. 319,1@- 13 Claims. (Qi. 10G-214) rlfhe present invention relates to a press and particularly to an improved press having a rolling bed for a Work piece.

While presses are known and in use, the subject invention is directed to a press with simple support .structure for the press to increase its load bearing and wear capabilities and having a rol-ling bed to greatly facilitate the positioning of the pieces of work to which the press is to be applied. The improved press design reduces the number and size of parts required for adequate support and at the same time improves the operation of and the ease in mounting of work on the same.

It is therefore an object of this invention to provide a press having a rolling bed to facilitaire positioning of pieces of work thereupon and having simplied construction to increase its load capacity and minimize manufacturing costs.

A further object or" this invention is to provide an improved press in which the bed construction is such as to permit the same to be rolled to a lateral position to facilitate application to and removal from of the pieces of work relative thereto.

Another object of this invention is to provide an improved press with `shear support plates to simplify the base structure and the bed structure of the press and to provide an improved structure to take the load off the connecting parts.

Still another object of the invention is to provide an improved press having greater load bearing capabilities.

These and other objects of this invention will become more apparent from the reading of the attached description together with the 4drawings wherein:

FIG. l is a right end elevation view of the improved press having a rolling bed with parts broken away;

FIG. 2 is a side elevation View of the improved press having a rolling bed with parts broken away;

FIG. 3 is a plan view of a supporting part with the improved press;

FIG. 4 is a plan view of an eccentric shaft for positioning the bolster bed of the improved press;

FIG. 5 is ra schematic drawing ofthe cable assembly for the improved press;

`FIG. 6 is a perspective View of the improved press having a rolling bed;

FIG. 7 is a portion of a side elevation view of the improved press showing an alternate construction of some of the parts; and

FIG. S is a sectional view'of the portionof the irnproved press taken along the lines 8 8 in FIG. 7.

Our improved'press is shown in perspective in FIG. 6 with the details of the same being apparent from the side and end elevational views of FiGS. 1 and 2. As will be seenin FIGS. l and 2, the improved press is comprised ot a base structure or member, indicated generally `at lil, which base member is made up of four angle iron corner posts 12 that are connected to form side `sections of the base member through a plurality of support rods or bars 20 which extend through holes inthe angle iron posts and are secured thereto by nut means 22 threaded onto the threaded extremities 23 of the rods. Further, the rods 2t) include spacer members 24 and 3l iitting over'the same. This structure, which will be best seen in FIGS. 1 and 6, providers the load bearing support for the base in a shear direction. The individual side sections which are madel up by two corner posts l2 with three rods 2li connecting the same are identiied in FIG. 2 at 2S .and Z9 respectively, and these side sections are connected together and spaced apart by elongated base plates which are secured respectively to the side sections by angle iron brackets vthrough suitable means, such as by bolt 'type connections 3S and welding as at dit. The base plate 30 are adapted to rest on the surface in which the press is to be positioned, such as a floor, to provide a level founda- `tion for the same.

The base structure or base member l@ of the press supports and positions a pair of upright frame members 45, 46, each of which is formed by a pair of elongated plates connected together by a third elongated plate member Si? at the upper extremities thereof, as seen in FlGS. l and 2. T he frame parts 4S and t9 are connected together througli the clamping action of nuts Sd threaded onto the reduced threaded extremities 5l of a spacer shaft 52 which serves also to space .the upright frame members t5 and ed at `their upper extremity. These frame memers are mounted on the rods 20 and are spaced apart through the spacer sleeves or members 2d mounted on the rods which sleeves abut against the sides ot 'the plates @E torininfr the upright frame members 45, 46. As will r be noted in FlGS. 1 and 2, the upright frame members 45, L which form `an upright or upstanding frame are mounted on the base member in such a manner that their open extremities do not touch the surface upon which the press is mounted, and hence all of the weight of and thrust imparted from the upright frame members will be transmitted through the mounting rods Ztl forming a part of the sides 28, 29 ofthe base member.

These two spaced frame members form the opstanding frame for the press which is generally U-shaped in form yand is designed to mount a cross-head member, indicated generally at ed, which extends between and is mounted on the sides of the frame members 45, 46 being positioned therebetween. The cross-head member 6@ generally provides a mounting for a tool for the press, as will `be later noted, and is designed to be moved up and down within the upstanding frame to accommodate the various sizes of work to be handled by the press. This cross-head member, as seen in FIGS. 1 and 2, is formed of a parir of end plates secured `to a pair of side plates e6 extending between the plates '4S of the frame members 45 and 46 to provide a generaliy box-like structure or frame which is open at its top and bottom for positioning a motor and tool therein. Thus, as will be seen in EEG. 1, the side plates 6d are suitably attached to the end plates o5 through screw means, indicated in phantom at 7G, and the side plates 66 extend beyond the end plates 65 and have holes or apertures therein as at 72 with these extensions .sliding between the plates 48 forming the upright frame members 4S and 4d. The bottom of this box-like or rectangular frame mounts a tool carrying frame formed by a plate 75 with an aperture 76 therein and upwardly extending ploite-like iiange members '78 having rollers 79 journalled in the upper corners thereof with the plate members 7S or flanges being secured `to the plate 75 through screw means indicated at 4di). The rollers '79 ride on rails 82 welded or suitably secured to the side plates 66 of lthe cross-head member to permit the tool carrying frame on the cross-head member to roll along the extent of the side plates on the cross-head member and position the tool carried by the cross-head member between the sides of the frame members 45 and i6 for locating of the tool translationally within the press. FIGS. l and 2 show in phantom, as at 85, a cylindrieally shaped hydraulic actuator which is positioned within the cross-head member and is adapted lto be mounted on the base plate 75 thereof through suitable screw means, such as shown in phantom at it. The end plates o5 of the Vin FIG. 1.

cross-head member mount pulleys 90 and 91 at one end of the cross-head member and 92, 93 on the other end of the cross-head member which pulleys are adapted to cooperate with a cable and winch system, to be later described, which positions the cross-head member Within the upstanding frame.

The cross-head member, when moved to a desired position Within the upstanding frame, is retained therein through suitable locking bars or shafts 95 which extend through spaced holes 98 in `the plates 48 of the frame members 45 and 46 and through the holes 72 in the side plate 66 of the cross-head which align therewith. These pins or rods will be removed when it is desired to change the position of the cross-head member 6i! on the upstanding frame and will be repositioned through the aligned holes in the plates of the frame members and cross-head member when a desi-red position or relationship between the two is obtained. Similarly, the tool carrying frame of the cross-head member at the llange pla-te 78 thereof includes .a set'or locking screw 100 (best seen in FIGS. 2 and 6) which secures the plate 75 and tool in a position on the cross-head member 60 after adjustment of the same .has been made. The screw G 'threads through a portion of the ange plate 7S and engages the rail 82 to provide a lock for this portion of the apparatus.

FIG. 6 shows a winch 11i) mount-ed on the plates 48 of the frame members 45 and 46 which is suitably secured thereon by means, such as screws 112. This winch opcrates a pulley system for positioning the cross-head member within the upright frame members. A pair of cables 115, 116 extend from the gear driven winch 110, which is rotated by a handle means 120, and are threaded across pulleys 121, 122 at one corner of the frame members 4S, 46. The pulleys are mounted on one of the spacing and connecting shafts 52 in a pulley arrangem-ent which is shown schematically in FIG. 5. A pulley 125 is positioncd at the other corner of the upright frame and is mounted on the spacer shaft 52 which will be best seen In addition, the spacer shaft 52 at this other corner mounts a bracket 128 and pulley 129 intermediate its extent, which will also be seen in FIG. 1. A similar pulley 130 is included on the spacer member 52 on the other side of the frame members. These pulleys cooperate with the pulleys 90, 91, 92 .and 93 on the ends of the cross-head member 66 for adjusting the position of the cross-head member within the upstanding frame. Thus, as will be seen in the schematic pulley diagram of FIG. 5,

the cable 115 from the winch 110 will thread across theY pulley 121V in one corner of the upstanding frame and down to the pulley 93 on the cross-head member, back to the centrally located pulley 136 at the same corner of the upstanding frame which is positioned on the spacer shaft 52, down to the pulley 92 on the other corner of the cross-head member and back to an anchor 132 (see FIG. 2) on one corner of the upright frame member 45 and attached to one of the side plates 43. The second cable 116 will thread across the pulley 122 in the same upper corner of the upstanding frame positioned on the opposite end of the spacing bar S2, across the top of the upright frame members to the pulley 125 at the opposite corner of the upstanding frame, down to the pulley 90 on the cross-head member 60, up to the pulley 129 mounted on the spacer member 52 of this end of the upstanding frame, down to the pulley 91 on the end plate of the crosshead member on this extremity of the cross-head member and back to an anchor indicated at 133 on the plate 48 of the frame member 45, as will be seen in FIG. l. As the Winch handle 125) is rotated, these cables will be wound on the drum of the winch 110 and the ends of the crosshead member 60 will be raised within or between the upright frame members 45, 46 of the upstandng frame for positioning the cross-head and the tool thereon.

The cross-head member 60 is thus adjustable to permit positioning a Work piece on the base member 10 of the press, which work piece will be positioned on a bed bolster, shown in FIG. 1 as composed of bolster parts 141 and 142. Each of the bolster parts are identical in construction and are adjustably positioned relative to one another as will be hereinafter described. The bolster provides the bed upon which the work piece is mounted, and each of the parts are formed bygside plates 145 positioned on either side of the elongated center plate 146 and suitably secured thereto as by welding. The side plates extend beyond the center plate 146, as will be best seen in FIG. 2, and .at the extremities of the side plates 145 are positioned mounting blocks 150 which extend 'translationally with respect lto the extent of the parts of the bed and provide a mounting surface, as at 152, for th-e bed on side plates 160 positioned on each of the side sections 28, 29 of the base member 10. The parts of the bolster bed are spaced apart, as -will be seen in F-IG. 1, `and are adjustable in this spacing through suitable screw means indicated at 170 on either end of the bed parts to control the bed spread to hold work pieces of different sizes. Thus, these parts of if the bolster bed are assembled or connected in a spaced relationship by screw means 170 and are supported at their extremities through enga-gement of the support blocks von :side plates of each section of lthe base member.

The side plates 160 extend between and are connected to the corner posts 12 of the base member through nut and bolt connecting means as at 165. The support plates 160 also mount stop brackets 172 at the upper extremities thereof, for purposes to be later noted. These support plates, in addition to being secured to the corner posts 12, are also connected through suitable metal' screw means to the elongated plates 4S of the upright frame members 45, 46. These connections between the support plates 160 on either section of the base member are used basically for positioning the support plates on ,the base vmember withl the load thereon from the bed Vright frame members 45, 46. These bars are held in position by the spacing sleeves 31, which are positioned between the ange of the corner posts and the shear bars on the rods 20, to complete the spacing arrangement for the upright frame members 45, 46 and the shear bars in the base member 10. Thus, as will be seen in FIGS. 2 and 6, the inwardly extending flange portions 182 of the shear bars 180, two of which are included in each side section of the base member, project beyond the profile of the elongated plates 48 of the frame' members and under the lower'surface of the support plates 160, for transmitting the force from the bed bolster transmitted to the support plates 160 to the rods 20. The mounting of the shear bars on the rods will insure that this force or load will be absorbed by the bars 20 in the base member 10.' This support will be in the shear direction and will prevent deformation or breaking of the bolt structures 165 and 175 which position the support plates 160 on the base member and upright frame members.

Also positioned on the surface of Vthe support members 160 are cam bars 190 (see enlargement of portion of FIG. 2) which extend along the support plates 160 substantially parallel -to the upper surface thereof. The bars cooperate with rollers 195 which are mounted on theV bed bolster center plates 146 through suitable brackets 197 and are secured on the plates 146 through large bolts 198 and small shear bolts 198. Bolts 198 are designed to shear underload, for purposes to be later noted. In the normal position of the hydraulic press, the rollers are out of contact with the cam bars 190 and the bed bolster parts will be positioned on the supk75J port plates 160 through the support blocks 150. The

cam bars 190 are adapted to be adjusted in position on the support plates 165 to engage and raise the bed bolster parts 141, 142 as an assembly, so that the bed bolster may be moved on the cam bars relative to the base member' and upstanding frame.

As will be seen in FIG. 2, cam bars 19t? are mounted on the eccentric portion 25) of an eccentric shaft 202, one of which is shown in detail in FIG. 4. The eccentric portion 250 is journallcd in the cam bar through suitable bearing means such as indicated by the sleeve 253 therein, with the shaft portion of the eccentric shaft 202 extending through apertures (not shown) in the support plates and terminating in a handle means 205 positioned beyond the surface of the base member. The cam bars 19@ are secured to the eccentric portions 269 of the eccentric shaft 252 by suitable locking means, such as a collar 204 which is welded or suitably secured to the extremity of the shaft. Thus, when the eccentric shafts 202 are rotated 180 degrees of angular rotation by a handle means 205, the cam bars 19) will be moved by virtue of rotation or the eccentric portion 200 on the shaft to engage the rollers 195 on the bed bolster parts, raising the bed bolster with its supporting blocks 150 at the extremities thereof ofi of the support plates 165 and permitting rolling motion of the entire bed bolster assembly along the cam bars and away from under the crosshead member to permit mounting of work pieces on the bed bolster without interference from the ups-tanding frame of the improved press. Movement of the bed bolster on the cam bars 19t) is limited by the stops 172 on the support plates 165 which extend beyond and engage the support blocks on the bed bolster as the bolster reaches the end of its travel on the cam bars. Thus the improved rolling press has a base member which permits movement of the bed bolster thereon to facilitate mounting of a work piece on the bed bolster, and the bolster parts are adjustable in spacing to accommodate any size work through the operation of the adjusting screws 17) connecting the bed parts in a side by side relationship. In the event that a load from the tool and hydraulic actuator is appl-led to the bed bolster parts 141, 142 when it is in the rolling or raised position, such a force will be transmitted to the side support plates 16) through the rollers 195 and cam bars 196. To prevent such a load from damaging these parts, the roller brackets 197 are attached to plates 146 through the large bolts 198 and the small shear bolts 198. Under such a load, the small shear bolts 198 will be sheared off allowing brackets 197 kto pivot about bolts 198 and the bed Ibolster parts to drop to a point where the supporting blocks 150 on the bolster parts 141, 142 engage the surface of the support plates 160 to take up the load.

The alternate construction of a portion of the press as shown in FIGS. 7 and 8 relates to the adjustment mechanism for the bed bolster parts 141, 142. In FIGS. 2 and 6, these parts were adjustably positioned relative ,to one another throughtwo adjustable screw means 170. In FIGS. 7 and 8, the screw'means has been modified, as indicated at 215, to 'provide a portion 211 extending beyond the face yof the bolster part 142. Two such screw means are utilized and they are positioned near the ends of the bolster parts 141 and 142 extending between the same. Thus, as will be seen in FIG. 8, the projecting portion 211 of the screw means has a squared extremity 212 which is adapted to mount an operating handle 215 with a similar shaped hole therein. The screw means 210 on either side of the bed bolster extend through the bolster parts 141, 142 at the plates 146 through apertures 216 and 2313 therein. The screw means 210 are threaded along their extent, as indicated at 225, and are positioned with respect to the bolster part 142 through a collar 217 which is keyed thereon, as at 21S. The bolster part 141 has nuts 224 welded to the plates 146 adjacent the apertures 230, and the threaded extremi es 220 of the screw means 210 extend therethrough to thread into these nuts. A gear or sprocket 232 keyed to the screw means 21) is positioned adjacent the surface of the plate 146 of the bolster part 142 at the extremities thereof, as will be seen in FIG. 8. These gears 232 are positioned on the opposite surface of the plate from the collars 217 and position the screw means 21@ relative to the bolster part 142. A chain 240 con nects the respective gears or sprockets on the bolster part 142 such that the respective screw means will move in unison upon rotation of either of fthe screw means.

This arrangement of parts will provide for adjustment of the spacing of the bolster parts 141, 142 through the screw means 210 in such a lmanner that both extremities of the bolster parts will be moved toward or away from one another simultaneously and at 4the same rate through the operation of a single handle 215. This w-ill keep the bolster parts aligned and simplify the adjustment of the bolster bed spread to facilitate mounting of various sized work pieces thereon.

The operation of the improved press is largely conventional. The improvements therein reside in the strucA tural details which provide a rolling bed bolster and per4 mits greater loads to be borne by the bed bolster of the press which is supported through improved shear type mounting means within the base member. The cross head member is adjustable on the upstanding frame to permit any size work to be positioned on the bed bolster, and the working tool mounted on Vthe cross head member may be adjusted along the cross-head member to permit the tool to work on any portion of the bed bolster or a part located thereon. This bed bolster 'may be raised from its mounting on the base member and rolled along the adjustable cam bars to a laterally disposed outof-way position to facilitate mounting of work pieces thereon. The structure for rolling the bed bolster also includes provisions for preventing damage to the same vthrough application of force to the bolster bed in the rolling position. In addition, the spread of the bed bol ster parts may be adjusted Vthrough screw means positioned therein, or as indicated in the alternate construction, through an improved adjusting mechanism which insures simultaneous movement of the bed parts in such a way as to prevent binding of the bed supporting struc ture. The mounting structures for the bed bolster and the cam bars are simple in design and provide a support structure to improve the operation and life of the press. Further, the simplicity in structure reduces the overall cost of the apparatus while increasing its load-bearing capabilities. Therefore, in considering this invention, it should be remembered that the present disclosure is illus trative only and the scope `of qthe invention should be determined by the appended claims.

We claim:

l. A press comprising in combination;

(a) a pair of spaced upright frame members,

(b) a cross-head member positioned between the spaced upright frame members,

(c) means slidably mounting 'and positioning said lc)ross-headrnember between said upright frame memers,

(d) means adapted `to mount a tool and actuator mounted on said cross-head member for movement along the extent of and between said spaced upright frame members,

(e) a base member including two side support sections for mounting said spaced upright frame members with the frame members being positioned generally midway along the extent of each of said side support sections and extending translationally therefrom,

() a plurality of mounting rod means included in the side sections of said base member and extending through the extremities of said upright frame members to secure the same,

`amistosa 7 (g) a support plate positioned on each of the side support sections of said base member extending along the extent of the same and having a'load bearing surface on the upper edge of the same,

(lz) a bolster bed includingia pair of relatively movable parts having load bearing surfaces at the extremities thereof positioned between said support plates and normally resting on said load bearing surfaces thereon,

(i) a plurality of shear bars including ange like projections mounted in said side support sections of said base member with said flange projections supporting said support plates on said side support sections of said base member and with certain of said mounting rod means extending therethrough to supportrthe same, A

(i) a cam bar positioned on each of said support plates and extending along the extent of the same,

(k) eccentric shaft means positioned through said support platesand mounting said cam bars for movement on the surface of said support plates, and

(l) roller means positioned on a surface of said bolster bed remote from said load bearing surfaces and adapted to ride on said cam bars to move said bolster bed along said support plates toward and away from said upright frame members, the eccentric shaft means in said cam barsl being adapted when rotated to raise said cam bars on said Asupport plates and lift said bolster bed oi of theload'bearing surface of said support plates to permit engagement of said roller means with said cam bars and movement of said bolster bed thereon.

2. The press of claim 1 'in which the means slidably mounting and positioning the cross-head member between the upright frame members includes a winch and pulley means connected to said. cross-head member and supported in part on said frame members.

3. The press of claim 2.and including locking means extending through said upright frame members and said cross-head member to hold said cross-head member in selected positions on said upright frame members.

4. The press of claim 3 'in whichV the relatively movable parts of saidbolster 'bed are connected together v through screw means adapted to adjust the spacing'therebetween on said support plates.

5. The press of claim 4 in which the support plates are positioned on the side support sections of said base member through bolt means and the shear bars are positioned parallel to'and adjacent the upright frame members with said flange projections extending under the surface of said support plates to resist forces applied to said bolster `bed and said support plates preventing shearing of said bolt mean. I

6. The press f claim 4 in which theV screw means 8 extendthrough said upright frame' to support and position the same 0n said base member, a member for carryving a tool mounted on said upright frame, support plates positioned on the side sections of said base member, a plurality of shear bar means mounted in said side sections of said base member on said load bearing rods and each having a surface that is positioned to support the support plates in said base member, a bolster bed positioned between the side sections on said base member and supported at its extremities on said support plates, roller means positioned on the extremities of said bolster bed, a movable cam bar for each support plate, eccentric means being journalled in said support plates and mounting said cam bars on said support plates from movement thereon, said eccentric means upon rotation being operative to move said cam bars to a position where they engage the roller means on said bolster bed and raise the bolster bed out of engagement at its extremities with said vsupport plates to permit rolling of said bolster bed on for moving the cam bars include at least a pair of eccentric shafts journalled in said support plates with an eccentric part journalled in said cam bars near the extremities thereof.

11. The press of claim 7 in which the plurality of shear bars are a pair of plates positioned on either side of said upright frame in each of said side sections of said base member Vand include a ilangeV portion projecting beyond connected through the bolster bed parts is a pair of drive -v screws having sprockets thereon connected together by a chain for simultaneous and identical operation of the pair of screws.

7. A press comprising, a base member adapted to be extending away from said base member normal to said Y surface, said base member having generally two side sections with a plurality of load bearing rods therein which said upright frame and under said support plates to resist the load imparted to said support plates from said bolster bed.

12. The press of claim 1 in which each of the roller means are releasably and pivotally mounted on the surface of the bolster bed through connection means which allow the roller means to pivot on their mountings on the surface of the bolster bed when the bolster bed is lifted from the load bearing surface of saidsupport plates and a predetermined load is applied thereto to prevent injury lto the roller means.

13. The-press of claim 7 in which the bolster bed includes a pair of -bed parts which are connected together by a pair of adjustable screw means positioned near the extremitiesof the bolster bed with the screw means being connected for simultaneous and identical movements.

References Cited in the file of this patent UNITED STATES PATENTS Georgeff Nov. 19, 1963 

1. A PRESS COMPRISING IN COMBINATION; (A) A PAIR OF SPACED UPRIGHT FRAME MEMBERS, (B) A CROSS-HEAD MEMBER POSITIONED BETWEEN THE SPACED UPRIGHT FRAME MEMBERS, (C) MEANS SLIDABLY MOUNTING AND POSITIONED SAID CROSS-HEAD MEMBER BETWEEN SAID UPRIGHT FRAME MEMBERS, (D) MEANS ADAPTED TO MOUNT A TOOL AND ACTUATOR MOUNTED ON SAID CROSS-HEAD MEMBER FOR MOVEMENT ALONG THE EXTENT OF AND BETWEEN SAID SPACED UPRIGHT FRAME MEMBERS, (E) A BASE MEMBER INCLUDING TWO SIDE SUPPORT SECTIONS FOR MOUNTING SAID SPACED UPRIGHT FRAME MEMBERTS WITH THE FRAME MEMBERS BEING POSITIONED GENERALLY MIDWAY ALONG THE EXTENT OF EACH OF SAID SIDE SUPPORT SECTIONS AND EXTENDING TRANSLATIONALLY THEREFROM, (F) A PLURALITY OF MOUNTING ROD MEANS INCLUDED IN THE SIDE SECTIONS OF SAID BASE MEMBER AND EXTENDING THROUGH THE EXTREMITIES OF SAID UPRIGHT FRAME MEMBERS TO SECURE THE SAME, (G) A SUPPORT PLATE POSITIONED ON EACH OF THE SIDE SUPPORT SECTIONS OF SAID BASE MEMBER EXTENDING ALONG THE EXTENT OF THE SAME AND HAVING A LOAD BEARING SURFACE ON THE UPPER EDGE OF THE SAME, (H) A BOLSTER BED INCLUDING A PAIR OF RELATIVELY MOVABLE PARTS HAVING LOAD BEARING SURFACES AT THE EXTREMITIES THEREOF POSITIONED BETWEEN SAID SUPPORT PLATES AND NORMALLY RESTING ON SAID LOAD BEARING SURFACES THEREON, (I) A PLURALITY OF SHEAR BARS INCLUDING FLANGE LIKE PROJECTIONS MOUNTED IN SAID SIDE SUPPORT SECTIONS OF SAID BASE MEMBER WITH SAID FLANGE PROJECTIONS SUPPORTING SAID SUPPORT PLATES ON SAID SIDE SUPPORT SECTIONS OF SAID BASE MEMBER AND WITH CERTAIN OF SAID MOUNTING ROD MEANS EXTENDING THERETHROUGH TO SUPPORT THE SAME, (J) A CAM BAR POSITIONED ON EACH OF SAID SUPPORT PLATES AND EXTENDING ALONG THE EXTENT OF THE SAME, (K) ECCENTRIC SHAFT MEANS POSITIONED THROUGH SAID SUPPORT PLATES AND MOUNTING SAID CAM BARS FOR MOVEMENT ON THE SURFACE OF SAID SUPPORT PLATES, AND (L) ROLLER MEANS POSITIONED ON A SURFACE OF SAID BOLSTER BED REMOTE FROM SAID LOAD BEARING SURFACES AND ADAPTED TO RIDE ON SAID CAM BARS TO MOVE SAID BOLSTER BED ALONG SAID SUPPORT PLATES TOWARD AND AWAY FROM SAID UPRIGHT FRAME MEMBERS, THE ECCENTRIC SHAFT MEANS IN SAID CAM BARS BEING ADAPTED WHEN ROTATED TO RAISE SAID CAM BARS ON SAID SUPPORT PLATES AND LIFT SAID BOLSTER BED OFF OF THE LOAD BEARING SURFACE OF SAID SUPPORT PLATES TO PERMIT ENGAGEMENT OF SAID ROLLER MEANS WITH SAID CAM BARS AND MOVEMENT OF SAID BOLSTER BED THEREON. 